Process of treating phosphoric acid to be used as a clarifier.



UNITED STATES PATENT OFFICE.

TAKAKAZU HAYASHI AND UMEJ'IRO EMURA, OF TOKYO, JAPAN, ASSIGNOIBS OF FIFTY ONE-HUNDREDTHS TO KWANTO SANSO KAIBUSHIKI KAISHA, LTD., 01 TOKYO, JAPAN.

A PROCESS OF TREATING PHOSPHORIC ACID TO BE USED AS A. CLARIFIER.

No Drawing.

To all whom it may concern:

Be it known that we, TAKAKAZU HAYASHI and UMEJIRO EMURA, subjectspf the Emperor of Japan, the former residlng atNo. 134 Komagome Hayashicho, Hongo, To 9,

and the latter at No. 67 Takinokawa, Ta 1- nokawamachi, Kitatoshimagun, Tokyo, Japan, have invented certain new and useful Improvements in Processes of Treating Phosphoric Acid to be Used as a Clanfier, of which the following is a specificatlon.

This invention relates to an improvement in a process of treating phosphoric acid to be used as a clarifier for treating sugar solution and consists in mixing a dilute solution of phosphoric'acid such as 1s used for that purpose, with a suitable quant ty of one or more calcium, aluminum or their salt or salts, heating the mixture to thereby cause the greater part of the free sulfurlc acid, which is contained in the said dilute solutlon as an impurity, to react with the said calcium, aluminum or their salt or salts in order to produce the corresponding sulfate or sulfates, removing a large quantity of the a Water contained in the solution, by concentration in 'vacuo, then adding a suitable quantity of carbonaceous substances to be used as decolorizing substances for sugar purification, this latter being used in such amount as to produce a seml-solid mixture, and finally recoverin the carbonaceous substances from the resi ue containing impurities after the treatment of the sugar solution, such recovering operation necessarily including a washing with a solution of phosphoric acid or phosphate orphosphates, so that the said substances'are brought into condition to be used again. The object of this invention is toet simultaneously, the two results of clari ying and decolorlzing sugar solutions, and to secure therewith a decrease in the cost of producing the mixed clarifier therefor by repeatedly using the carbonaceous substance or substances after recovering.

We will now roceed to explain the invention more ful y.

This invention relates to a process of treating hosphoric acid to be used as for the clan ying of sugar solutions, and more especially of subsequently mixing the stud Specification. of Iietters Patent.

Patented June 11, 1918.

Application filed May 24, 1917. Serial No. 170,805.

phosphoric acid with one or more carbonaceous substances suitable for decolorizing sugar, for instance, bone black. The invention ischaracterized by the further treatment of the said mixed clarifier, so as to make use of such used and recovered carbonaceous substance, the urification of the recovered carbonaceous substance necessarily includin thestep of washing with a solutionof 'p osphoric acid or of a phosphate or phosphates. v

The dilute solution of phosphoric acid employed for this invention must be quite free from sulfuric acid, which impurity is difiicult to avoid being usually contained in commercial phosphoric acid such as is generally used in the sugar industry. The perfect elimination of free sulfuric acid contained in commercial phosphoric acid may be achieved in any suitable method, but the preferred method therefor is to mix the dilute solution of commercial phosph ic acid with a suitable quantity of a calc um or aluminum salt or salts, or other com und, then to heat the mixture up to a suflic'i ntly high temperature to cause the said free sulfuric acid to combine with the said calcium or aluminum to produce the sulfate of one or both of these metals. This purified solution of phosphoric acid is then freed from the greater part of its water by concentra tion in a vacuum. When this solution is moderately concentrated one or more car- J the purification of the sugar solution is largely lost. Therefore in our invention this carbon is recovered by the process hereinafter set forth. In such recovery this recovered carbonaceous decolorizing agent (or agents) is washed with a'solution of phosphoric acid orof its salt or salts. Of course the residue of the bone black mixture, after the treatment of raw sugar solution purlfied by the said. mixture of phosphoric acid and carbonaceous subst nce, contalns more or less calcium, whi has been necessarily added to the sugar solution in the first step of .purifying operation thereof, this being in the form-of phosphate insoluble in water, and also contalns many other impurities as will be apparent. The most common method of recovering the decolorizing agents from such a residue is to heat it without access of air. the calcium content cannot be eliminated. Therefore in the present invention this burnt product may be washed with dilute phosphoric acid or its salts in order to produce acid phosphate of lime, which is s0lu V ble in water and thus the calcium content water or hot water, etc., is supp a pipe at the center of said filter and after the washing operation, the supplyv of the liquid is stopped, the spinning of the filter be1n continued until the material is dry, whic requires only a few minutes.

A specific example of this invention is given, as follows A dilute solution of. industrial or commercial phosphoric acid (obtained by treating phosphorite or bone black with sulfuric acid and filtration, said solution containing from 13 to 20 per cent. of phosphoric acid) is mixed with from 3 to 10 per cent. of aluminum or from 5 to 13' per cent. of aluminum hydroxid. This mixture is heated froml to 2 hours to a temperature of from 60 to C. The aluminum, under theaction of the heat, combines with the sulfuric acid contained in said solution. of phosphoric acid and the free sulfuricacid is thereby removed. The solution is concentrated by vacuum distillation.

Powdered bone black or similar carbonaceous decolorizing substance is then added in amount suflicient to obtain a semi-solid mixture constituting the final product. The quantity of such carbonaceous substance to be added may be widely varied and may for instance be equal to one-half the quantity oflie clarifier itself, (2'. e. the phosphoric aci This product can then be used as a clarifier for sugar solution in the same manner But" by such a 'procedure only,"

- finall as pure phosphoric acid clarifier, the sugar solution being at first stirred wlth the ad dition of milk of lime in the usual manner. The new clarifier is thereafteg, added, and the quantity thereof may be varied according to the percentage of impurities contained in the sugar solution to be purified.

To recover carbonaceous decolorizing agent from the residue obtained after the treatment of sugar solution by the above mentioned clarifier, one or more of the following methods are used according to the condition of the residue. (First). When the quantity of impurities is relatively small (for instance, when the recovering operation has been repeated only a few times), the residue is washed with a solution of phosphoric acid of 2 to 5 B., or of phosphate or phosphates and then washed with hot water and dried.

- (Second). When the quantity of impurities is somewhat greater, for instance, when the recovering operation is on material which has been used from four toseven times, the residue is heated in a steam jacketed vessel, together with a caustic soda solution of 5 to10 B., or is heated b direct steam. After a suitable heating t e substance is taken to a centrifugal filter and water and steam are supplied from the center of the centrifugal filter, while it is continuously rotated. After one or two hours, the supply of water and steam is cut ofl, and the mass washed with a solution of phosphoric acid or phosphate or phosphates of 5 to 7 136., after which. agaln washed with hot water in the same manner and dried.

(T 'rd). When the quantity of impurities is'considerably greater, the residue is first heated sufliciently to char the organic material present, then washed with a solution of phosphoric acid or a phosphate of 10 or 15 B., andfinall dried.

The carbonaceous su stance remaining from the above-mentioned method and accordingly containing practically no impurities or only very small quantities thereof, can be used again for mixing with the phosphoric acid purified and concentrated as above described for treatment of sugar solution. Moreover, when the residue is treated by the third method above mentioned, the

sO-treated material may be further treated by the first or the second method, thus ening the decolorizing agent or agents to be used almost permanently.

In carrying out the recovering operation according to the above mentioned methods which constitute theessential points of the invention, the best result is obtained when the recovered decolorizing agent is further washed by a dilute water solution of sulfurou's gas or of sulfite or sulfites- This washing operation is preferably conducted 1 just before the drying operation but in some cases may precede the phOSPhOI'lC acid treatment (or phosphate treatment).

We claim: I,

1. A process of treatlng used carbonaceous sugar-purifying material, which comprises the steps of washing the same with dilute phosphoric acid and thereafter mixing the residue with a more concentrated phosphoric acid substantially free from splfuric acid, in such proportions as to produce a semi-solid mixture.

2. A process of. treating used carbonaceous sugar-purifying material, which comprises the steps of heating the same with caustic alkali so1ution,4and separatin .the resulting liquor, then washing with ilute phosphoric acid, and thereafter mixing the residue with a more concentrated phosphoric acid free from sulfunc acid in such proportions as to produce a semi-solid mixture.

3. A process of treating used carbonaceous sugar-puri ing material, which comprises the steps 0 first charring the organic substances in the material, thereafter washing the same with dilute phosphoric acid and thereafter mixing the residue with a more concentrated hosphoric acid substantially free from Sui furic acid, in such proportions as to produce a semi-solid mixture.

In testimony whereof we have hereunto set our hands in presence of two subscribing witnesses. r r r TAKAKAZU HAYASHI. UMEJIRO EMURA.

Witnesses:

GENJI KURIBARA, SUGAO SOGAS. 

